Japanese unexamined patent application publication No. JP-A-2006-267994 (Patent Document 1) describes a related art image forming apparatus. In the related art image forming apparatus, a process cartridge having a development cartridge is removably attached to a main unit casing. In the related art image forming apparatus, an attached process cartridge detects whether or not a development cartridge is new, thereby measuring the life of the development cartridge since when the development cartridge was determined to be new by detection.
For instance, the related art image forming apparatus has a development cartridge which includes a detection gear consisting of a cogless gear and contact projections formed on the detection gear, and has a main unit casing which includes an actuator and an optical sensor.
In the related art image forming apparatus, when the process cartridge is attached to the main unit casing, warm-up operation is started, and driving force is transmitted from a motor installed in the main unit casing to the development cartridge.
When the development cartridge is new, driving force for the cartridge is transmitted to the detection gear, the detection gear rotates. Thereupon, a contact projection comes into contact an actuator, and the actuator blocks detection light for an optical sensor.
In the meantime, when the development cartridge is old, driving force for the cartridge is not transmitted to the detection gear, and the detection gear is not rotated. Accordingly, the contact projection does not contact the actuator; hence, detection light for the optical sensor passes through the sensor.
A CPU provided in the main unit casing determines whether or not a development cartridge is new, by detection/nondetection of detection light for the optical sensor.